The long-term objective of this program is to elucidate the cellular aspects of enamel formation. The goals of the proposed project period are threefold: (1) to quantitate the morphological aspects of amelogenesis, (2) to perform ATPase and alkaline phosphatase determinations on the functionally differnt enamel organ cells, and (3) to investigate the presence of phosphatidylserine in the enamel organ. Item 1 will be accomplished by morphometric analysis of different parts of the enamel organ, with particular attention given to those parts of the maturation enamel organ which allow calcium to gain entry into the enamel and to those whch restrict calcium entry. Item 2 will be accomplished by the use of standard TEM histochemical procedures and the use of a variety of inhibitors for definitive identification of enzymes. Item 3 consists of isolating enamel organ cells and then performing PS determinations. These experiments, especially items 2 and 3, have been designed so that they can test a model for the transcellular transport of calcium that was proposed during the current project period.